Stator for electric machines

ABSTRACT

The present invention relates to a stator for an electrical machine, in particular an EC motor, comprising a plurality of metal sheets in the form of a packet of stacked laminations. Between each two poles of the stator, there is a respective joint region in which at least one recess is provided. The recess is embodied as a slot,-which extends at a predetermined angle (α) obliquely to a center axis of the stator.

PRIOR ART

The present invention relates to a stator for an electrical machine, inparticular an EC motor (electrically commutated motor), in which thestator is embodied of a plurality of laminations in the form of a packetof stacked laminations.

In a number of fields of application, electronically controlled electricmotors are gaining ever-increasing importance. These are electric motorsin which the requisite periodic switching of coils is no longer done bymeans of a commutator, but rather by electronic switch devices. Oneexample of electronic switch devices is a rotor position sensor forfinding when the stator and the rotor, for the coils that are to beswitched at that specific moment, are in a relative position that isfavorable to switching or that promotes switching.

From German Patent Disclosure DE 198 42 948 A1, an electric motor whichhas a stator produced from a lamination packet is known. The individualsheet-metal laminations have indentations so that adjacent laminationswill mesh with one another. The individual poles are joined together attheir pole pieces via a plurality of ribs, creating a rectilinear slot.The slot is formed of a plurality of short recesses, each separated bythe ribs. Because of the rectilinear embodiment of the slots and thehigh number of ribs, however, this known electric motor has a relativelyhigh locking moment and relatively low power.

ADVANTAGES OF THE INVENTION

The stator according to the invention for an electrical machine, inparticular an EC motor, is embodied such that because of an advantageousdesign of the slot, it has a very favorable locking moment. Moreover, anelectrical machine with a stator according to the invention has highpower. This is achieved according to the invention by providing thatslots between two poles of the stator are embodied such that they extendat a predetermined angle obliquely to a center axis of the stator.According to the invention, the oblique slots can be embodied incontinuous form, so that individual slots are not separated by ribs orthe like. Thus a very favorable locking moment and high power can beachieved. The stator according to the invention can furthermore beproduced very economically, since the stator can be formed of aplurality of laminations stacked one above the other that can beproduced by stamping, for instance. The individual laminations arestamped in such a way that when they are placed one above the other, theslot is created, extending at an angle to the center axis as viewedacross the height of the lamination packet. The stator packet issurrounded by a short-circuit ring, by way of which the flux flows.

To furnish a stator that is especially economical to produce, the slotsof the stator packet are embodied in stepped form. The height of eachstep is equivalent to the thickness of one lamination. The various slits(stamped recesses) in one lamination are offset from those of theadjacent lamination by a predetermined angle in the circumferentialdirection, so that when the lamination packet is assembled, an obliquelyextending, stepped slot is created; that is, the two long sides of theslot are in stairstep form.

In another preferred embodiment of the present invention, the slots ofthe stator lamination packet are linear, or in other words embodied withstraight long sides and a constant width.

To keep the number of ribs as low as possible, for the sake of attainingthe highest possible power, the stator packet and the short-circuit ringare preferably joined together by a positive-engagement joint. Thepositive engagement furthermore assures that the air gaps created willbe as small as possible, so as to keep the power losses as slight aspossible. The positive-engagement joint is preferably embodied at theend regions of the poles which protrude outward from the stator. By wayof example, the positive-engagement joint can be embodied as a dovetailjoint, a T-shaped joint, or any arbitrary positive-engagement joint.Either the protruding region of the joint at the poles of the stator andthe receiving region of the joint can be embodied on the short-circuitring, or the protruding region of the joint is embodied on theshort-circuit ring while the receiving region of the joint is at thepoles.

Preferably, the angle between the center axis of the stator and theobliquely positioned slot is between 15° and 20°, and especiallypreferably it is 18°.

A connection of the poles is preferably made such that in the uppermostand lowermost laminations of the stator lamination packet, there are noslits. As a result, improved stability of the lamination packet can alsobe achieved.

In another preferred embodiment of the present invention, a plurality ofoblique slots which are offset parallel from one another longitudinallyof the stator are formed between two poles. As a result, it is attainedthat the stator is mechanically more stable, but with an increasingnumber of the resultant additional connecting ribs, it loses power. Itshould be noted that if there are a plurality of slots, the slots can beembodied such that they partly overlap in the direction of the height ofthe stator lamination packet, or that between individual slots there isone lamination each without recesses, to improve the stability of thelamination packet.

In another preferred embodiment of the present invention, the obliqueslot according to the invention comprises a plurality of shorter slots,which are disposed in a row. The plurality of smaller slots is thusdisposed in a row, one after the other, and when made from metal sheetsis for instance separated by one sheet thickness each. From thestandpoint of production, such a slot can for instance be produced in asimple fashion by providing that individual laminations between thesmaller slots are not provided with a recess, so that the result is alinear arrangement having a plurality of short, oblique slits.

The lamination packet of the invention for the stator is preferably usedin an EC motor, in which windings are applied to the stator.

DRAWINGS

In the ensuing description, a plurality of exemplary embodiments of theinvention are described in detail.

Shown are:

FIG. 1, a schematic, perspective fragmentary view of a stator laminationpacket in a first exemplary embodiment of the present invention;

FIG. 2, a schematic perspective view of a stator lamination packet in asecond exemplary embodiment of the present invention;

FIG. 3, a perspective fragmentary view of the stator lamination packet,shown in FIG. 2, from a different angle; and

FIG. 4, a plan view on a stator lamination packet with a short-circuitring, in a third exemplary embodiment of the present invention.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

A stator 1 in a first exemplary embodiment of the present invention willnow be described, referring to FIG. 1.

As shown in FIG. 1, the stator 1 includes a plurality of toothlike,outward-oriented poles 2. Between each two adjacent poles is arespective joint region 3 of a lesser thickness. The stator laminationpacket is composed of a plurality of individual metal sheets, stackedone above the other. The sheets are preferably stamped out, making themeasy to produce in terms of manufacturing technology.

As can be seen from FIG. 1, continuous slots 4 are formed in each of thejoint regions 3. The slots 4 have a steplike or stairsteplike shape.This stepped shape is attained by providing that in the individualsheets, the recesses, which in the assembled state result in the slot 4,are each stamped out offset from one another by a certain angle in thecircumferential direction. Thus the height of each individual step ofthe slot 4 is equivalent to the thickness of one sheet. It should benoted that it is understood that a plurality of sheets disposed oneabove the other can instead all be provided with the same recess; inthat case, the step height of the slot is no longer the same as thesheet thickness but instead is the sum of the sheets stacked above oneanother that all have the same recess.

By means of this oblique position of the slot 4 in the stator 1, amarkedly improved locking moment can be attained. As can be seen fromFIG. 1, to improve the stability of the stator, the top sheet 5 of thelamination packet and the bottom sheet 6 of the lamination packet caneach be embodied without a recess. Since according to the invention theslots 4 are embodied in continuous form, or in other words the slots 4extend continuously from the bottom sheet 6 to the top sheet 5, veryhigh power can still be achieved.

As FIG. 1 shows, the slots 4 are disposed at an angle α of approximately20° to a center axis X-X of the stator 1. The slot 4 is embodied suchthat it does not directly adjoin the teeth of the poles 2 on both of itsends, but instead stays spaced apart from the poles 2 by a certaindistance.

In FIGS. 2 and 3, a stator in accordance with a second exemplaryembodiment of the present invention is shown. Elements that are the sameor functionally the same are identified by the same reference numeralsas in the first exemplary embodiment.

As shown in FIG. 2, the stator 1 essentially corresponds to the statorof the first exemplary embodiment. In a distinction from the firstexemplary embodiment, however, instead of one continuous slot 4 betweentwo adjacent pole teeth 2 at the joint regions 3, there are a pluralityof continuous slots 4, namely precisely four of them. To improve thestability of the stator 1, the slots 4 of a joint region 3 are disposedsuch that they do not overlap in the direction of the height of thestator, that is, in the direction of the center axis X-X. In otherwords, in the lamination packet, one sheet without a recess is disposedbetween each two adjacent slots 4. Because of the thus-formed ribsbetween the individual slots 4, the stator does lose some percentage ofits power, but is constructed mechanically more stably.

The slots 4 have a length such that they extend over a plurality ofsheets. In the exemplary embodiments shown in FIGS. 2 and 3, the slots 4have a height in the direction of the center axis X-X of the stator 1that is approximately equivalent to ⅕ the height of the total statorpacket.

As shown in FIG. 3, because of the embodiment of a plurality of slots 4in each joint region, it is possible for a tooth segment A between theslots to break off. To prevent this, in FIG. 4 a third exemplaryembodiment of the present invention is shown, in which once again thesame elements are identified by the same reference numerals.

To prevent a tooth segment A from breaking off, the toothed ring of thestator 1 is embodied such that it has dovetail-like protrusions 9 on theends of the poles 2. These dovetail-like protrusions 9 engagecomplementary recesses 8 that are formed on an inner circumference of ashort-circuit ring 7. Thus by means of positive engagement, the stator 1is firmly joined to the short-circuit ring 7. It is thereby assured thateach stator tooth segment A is likewise joined to the short-circuit ring7 by positive engagement and hence cannot break off.

It should be noted that instead of the dovetail-like positiveengagement, a T-shaped, L-shaped or circular-segmental positiveengagement, or other arbitrarily embodied geometric positiveengagements, are possible.

Thus the present invention relates to a stator for an electricalmachine, in particular an EC motor, comprising a plurality of metalsheets in the form of a packet of stacked laminations. Between each twopoles 2 of the stator 1 there is a respective joint region 3, in whichat least one recess 4 is provided. The recess is embodied as a slot,which extends at a predetermined angle α obliquely to a center axis X-Xof the stator.

The above description of the exemplary embodiments of the presentinvention is intended solely for illustrative purposes and not forlimiting the scope of the invention. Various changes and modificationsmay be made without departing from the scope of the invention or itsequivalents.

1-10. (canceled)
 11. A stator for an electrical machine, in particularan EC motor, comprising a stator having a plurability of poles (2) and aplurality of metal sheets in the form of a packet of stackedlaminations, a joint region (3) between each two poles (2) at least onerecess (4) disposed in each joint region (3) the recess (4) beingembodied as a slot which extends at a predetermined angle (α) obliquelyto a center axis (X-X) of the stator.
 12. The stator of claim 11,wherein the slots (4) in the stator lamination packet are embodied insteplike form.
 13. The stator of claim 11, wherein the slots (4) in thestator lamination packet are embodied linearly, with a constant width.14. The stator of claim 11, further comprising a positive-engagementjoint embodied between the stator lamination packet and a short-circuitring (7).
 15. The stator of claim 12, further comprising apositive-engagement joint embodied between the stator lamination packetand a short-circuit ring (7).
 16. The stator of claim 13, furthercomprising a positive-engagement joint embodied between the statorlamination packet and a short-circuit ring (7).
 17. The stator of claim14, wherein the positive-engagement joint is embodied as a dovetailjoint, a T-shaped joint, or an L-shaped joint.
 18. The stator of claim15, wherein the positive-engagement joint is embodied as a dovetailjoint, a T-shaped joint, or an L-shaped joint.
 19. The stator of claim16, wherein the positive-engagement joint is embodied as a dovetailjoint, a T-shaped joint, or an L-shaped joint.
 20. The stator of claim11, wherein the angle (α) between the center axis (X-X) of the statorand the slots (4) is between 15° and 20°.
 21. The stator of claim 12,wherein the angle (α) between the center axis (X-X) of the stator andthe slots (4) is between 15° and 20°.
 22. The stator of claim 13,wherein the angle (α) between the center axis (X-X) of the stator andthe slots (4) is between 15° and 20°.
 23. The stator of claim 14,wherein the angle (α) between the center axis (X-X) of the stator andthe slots (4) is between 15° and 20°.
 24. The stator of claim 11,wherein the uppermost lamination (5) of the stator lamination packet andthe lowermost lamination (6) of the stator lamination packet have noslits.
 25. The stator of claim 12, wherein the uppermost lamination (5)of the stator lamination packet and the lowermost lamination (6) of thestator lamination packet have no slits.
 26. The stator of claim 13,wherein the uppermost lamination (5) of the stator lamination packet andthe lowermost lamination (6) of the stator lamination packet have noslits.
 27. The stator of claim 11, wherein the recess formed between twopoles (2) in the joint region (3) is formed by a plurality of slots (4)which are offset parallel to one another in the direction of the centeraxis (X-X) of the stator.
 28. The stator of claim 12, wherein the recessformed between two poles (2) in the joint region (3) is formed by aplurality of slots (4) which are offset parallel to one another in thedirection of the center axis (X-X) of the stator.
 29. The stator ofclaim 13, wherein the recess formed between two poles (2) in the jointregion (3) is formed by a plurality of slots (4) which are offsetparallel to one another in the direction of the center axis (X-X) of thestator.
 30. The stator of claim 27, further comprising one lamination inwhich there are no slits in the stator lamination packet between each ofthe individual slots (4).
 31. The stator of claim 11, wherein the slot(4) comprises a plurality of slits disposed in a row.